Fix typo in v5.md (#8229)

Author: inokawa

docs/upgrading/v5.md

@@ -25,7 +25,7 @@ In general, the process looks like this:
 
 1. [Upgrade to React v16.8 or greater](#upgrade-to-react-v168)
 2. [Upgrade to React Router v5.1](#upgrade-to-react-router-v51)
-   - [Remove `<Redirect>`s inside `<Switch>`](#remove-directs-inside-switch)
+   - [Remove `<Redirect>`s inside `<Switch>`](#remove-redirects-inside-switch)
    - [Refactor custom `<Route>`s](#refactor-custom-routes)
 3. [Upgrade to React Router v6](#upgrade-to-react-router-v6)